Fastening devices

ABSTRACT

A two-part fastening device for fastening two panels together is provided with a rotatable drum (16) with at least one camming surface and a pin (10) with a head (14) formed to engage with the camming surface. The pin (10) is secured in one panel to be fastened and the rotatable drum positioned in the other panel. The head (14) of the pin is passed into the drum member which is then rotated so that the camming surface acts to pull the head of the pin inwardly, thus drawing the two panels together. The head (14) of the pin is provided with protrusions (22) which cooperate with the rotatable drum so that locking engagement of the fastening device can be achieved.

FIELD OF THE INVENTION

This invention relates to fastening devices for use in securing twofurniture panels together, and more particularly to two-part fasteningdevices comprising a pin for engagement with a rotatable locking drum.

BACKGROUND OF THE INVENTION

Fastening devices of this general type are well-known. They typicallycomprise a pin which is inserted into a surface of a first panel to apredetermined depth so that its head protrudes from the panel, and arotatable locking drum positioned in a recess in a second panel andarranged to receive the head of the pin. The panels are fastenedtogether by rotating the locking drum which, by means of internalcamming surfaces, pulls the head of the pin inwardly thus drawing thetwo panels together.

These known devices have disadvantages in that vibration, for exampleduring transport, can cause the rotating drum to rotate out of thelocking position, loosening the joint between the panels.

Prior art devices such as these also have the disadvantage that therotating drum must be fully turned to achieve the "locked" position.This requires accurate positioning of the recess which is to receive thedrum in the respective panel. If this recess is positioned too close tothe panel edge the panels will butt up against one another before thedrum has been turned to the fully locked position and therefore thejoint will readily come loose. Alternatively, with the recess too farfrom the edge of the panel the locked position will be reached beforethe panels make contact, so that a gap is left between them. Thetolerances for positioning the recess are very low; as little as 0.5 mmdeviation from the correct position can cause the problems outlinedabove.

A device intended to overcome these disadvantages is disclosed in U.S.Pat. No. 4,810,127 to Hettich. This fastening device is provided withaxially aligned ribs or saw-tooth shaped raised portions on thecircumferential surface of the rotating drum, and also has similarraised portions on the inner camming surface of the drum. Theseformations ensure that unintentional loosening of the fastening devicefrom the locked position is made substantially more difficult, and alsoprovide some facility for locking in positions other than the fullyturned position.

The Hettich camming drum does however have some disadvantages, inparticular associated with the saw-teeth portions on its outer surface.When the drum is turned more than once or twice in each direction thesaw-teeth start to wear away the inner surfaces of the recess in whichthe drum is placed, and can tend to make the hole oval. The saw-teethalso increases the torque which is required to turn the drum, making itmore difficult to turn. The result can be that the drum fells as if itis locked before the joint is secure.

Other problems can arise because of the forces exerted during turning ofthe rotatable drum. The underside of the head of the pin member and theinner camming surfaces of the drum have been angled, relative to the pinaxis, in prior art devices resulting in outwardly directed forcesexerted by the pin head on the cam, which can cause bursting of therotatable drum.

The invention aims to overcome, at least in part, some of thedisadvantages of the prior art just described.

SUMMARY OF THE DISCLOSURE

According to the invention there is provided a fastening device forjoining two panels together comprising an elongate pin member adapted tobe secured in a first one of said panels, the pin member including ahead portion arranged to protrude from said first panel, and a rotatabledrum member adapted for insertion in a recess in a major surface of theother panel and arranged to receive said head portion of the pin member,the drum member being provided with at least one camming surfacearranged to pull the head of the pin member inwardly into the drummember when said drum member is rotated and thereby fasten the panels,wherein the head of the pin member is provided with irregularitiesarranged to cooperate with the drum member to facilitate lockingengagement of the fastening device.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be better understood an embodimentthereof will be described, by way of example, with reference to theaccompanying drawings, wherein:

FIG. 1 is a side view of a pin member of a fastening device according tothe invention, the head of the pin being shown partly in section.

FIG. 2 is a sectional view taken along the line II--II' in FIG. 1.

FIG. 3 is a partial view of the pin member of FIG. 1 shown partly insection.

FIG. 4 is a perspective view of a rotatable drum member of a fasteningdevice according to the invention.

FIG. 5 is a side view of the rotatable drum member of FIG. 4 seen fromthe direction A.

FIG. 6 is a schematic view of a fastening device according to theinvention when in use for joining two panels together substantially atright angles to one another.

FIG. 7 is a detailed description of the preferred embodiments.

The pin 10 shown in FIG. 1 is generally of known configuration having alower portion comprising a threaded shank 12 and an upper portioncomprising a head 14 and smoothly contoured neck 16 and shoulder 18portions. The upper and lower portions of the pin 10 are separated by aflared skirt 20 which acts to prevent the pin 10 from being drivenbeyond a predetermined depth when it is driven into the edge of a firstpanel to be joined. The head 14 includes a screwdriver recess 15 in itstop surface to enable the pin 10 to be driven into the first panel by ascrewdriver.

The pin 10 may be manufactured in a die-casting process using an alloywhich comprises mainly zinc, with added copper, aluminium and tin. Suchan alloy is available commercially and is known by the trade name"Mazak" or "Zamag". Moulding the pin in this way, rather than using themore usual steel turned pin, enables the inclusion of certain featuresin the design which could not otherwise be readily incorporated. Forinstance the contoured neck 16 and flared skirt 20 already described aremore difficult to achieve by turning and would increase the cost ofmaking such a pin by turning considerably. The pin 10 includes otherfeatures which are achievable because of the use of a moulding processin the manufacture of the pin, to be described below.

As known from the prior art, the protruding upper portion of the pin 10is arranged to pass into a bore in the edge of the second panel to bejoined so that the head 14 is received in a rotatable drum memberpositioned in a recess in a major surface of that panel. The drum isthen rotated to secure the joint, as will be described in more detailbelow.

As can be seen in FIG. 1, the underside of the pin 10, where it adjoinsthe neck portion 16, is formed with a number of conical protrusions 22circumferentially spaced around the periphery of the pin head 14. In theillustrated embodiment the angular separation of the conical protrusionsaround the circumference of the head 14 is 30°. This can best be seen inthe view of the underside of the head, FIG. 2. Each of the conicalprotrusions 22 is in the form of a circular cone with an internal 90°angle at its apex and the axis of the cone positioned at 45° to the pinaxis. This arrangement can be seen in FIG. 3.

The effect of the described arrangement of cones 22 is to provide anumber of surfaces 23 on the underside of the head 14 which are in aplane substantially perpendicular to the axis of the pin 10, and toprovide a number of positions around the circumference of the undersideof the head which are substantially right-angled corners. These interactwith the rotatable drum 50 to provide a ratchet-type engagement in amanner to be described later.

In the arrangement of conical protrusions 22 shown in FIGS. 2 and 3,each of the cones is directed radially outwards with respect to the axisof the pin 10. This is the desired arrangement, but due to the practicalconsiderations of the manufacturing process it may not be achievable inexactly the form shown. When the pin is formed by die-casting twoprincipal mould parts will generally be used, which separate along aplane including the pin axis. The finished pin is extracted from themould by drawing the two mould parts away from each other in a directiongenerally perpendicular to the plane of separation. The "parting line"is shown as a vertical line in FIG. 2, and represents the position ofthe plane of separation. For separation of the mould parts to bepossible each of the conical protrusions on either side of the partingline at the top and bottom of FIG. 2 will be formed with a "tail"tapering back towards the parting line along the direction of separationof the mould parts. This is necessary to prevent the formation ofundercuts which would make withdrawal of the mould parts impossible.Similar considerations give rise to the surfaces 23 of each of theconical protrusions 22 being formed at 180° to the underside of the head14.

The provision of the surfaces 23 perpendicular to the pin axis meansthat the forces exerted during the camming action of the rotatable drumby the underside of the head 14 are no longer directed outwardly inrespect of the drum. The tendency for the drum to burst during cammingis therefore greatly reduced.

It may be supposed that these results could readily be achieved bymaking the whole of the underside of the head 14, where it protrudesbeyond the diameter of the neck portion 16, a flat surface so that theunderside and the sides of the head 14 meet at right angles all aroundthe circumference of the head 14. However, because of the brittle natureof the preferred alloy "Mazak" such an arrangement would be highlysusceptible to breaking forces. The use of the cone arrangement avoidsthis problem whilst still providing means for the engagement with therotatable drum 50 which is to be described.

However it is not intended that the invention be limited to the specificarrangement described above, nor to the protrusions 22 being conical,and it will be appreciated that any other suitable form of protrusionmay be adopted, as will be understood from the following description.

The rotating drum member 50 of a fastening device according to theinvention will now be described with reference to FIGS. 4 to 6 of theaccompanying drawings. As with prior art devices of this type, thegenerally cylindrical rotating drum is intended to be positioned in arecess close to an edge of a major surface of one of two panels to bejoined. In the figures the upper surface 52 of the drum member 50 isplaced into the recess first, and the depth of the recess is sufficientto allow the lower surface 54 to lie substantially flush with thesurface of the panel, as can be seen in FIG. 6.

However, the drum member 50 may alternatively be positioned in therecess so that the upper surface 52 lies flush with the surface of thepanel in which it is positioned. The cut-out portion of the uppersurface 52 which can be seen in FIG. 4 provides access for the head ofthe pin 10 from that surface of the panel. The fastening device cantherefore be used in situations where a panel containing several drummembers is to be fixed between two fixed upright panels, for instancewhen fitting a shelf. In such cases the pin 10 for each drum member 50is positioned in the relative upright panel and the shelf incorporatingthe drum members 50 can be lowered into the pins 10 in situ.

A bore is provided to connect the recess with the edge of the panel sothat, when the drum 50 is in position in the recess, the head 14 of thepin 10 described above can pass into the drum 50 through a mouth portion56. The lower surface 54 of the drum member 50 is provided with ascrewdriver recess (not shown) to enable the drum 50 to be turned oncethe screw head 14 is received inside it. The mouth 56 narrows to form aslot 58 which cuts through the wall of the cylindrical drum 50 andcontinues laterally around approximately half of the circumference ofthe drum 50.

The width of the upper and lower surfaces 60, 62, gradually increasesfrom almost nothing along the slot 58 moving away from the mouth portion56 as can be seen in FIG. 4, and camming surfaces 66 and 68 which are ofsimilar form and are located above and below the slot (see FIGS. 4 and5) follow the line of the inner edge of surfaces 60, 62.

When the drum 50 is rotated the ends of the camming surfaces 66, 68adjacent the mouth portion 56 move between the underside of the head 14and the panel in which the pin 10 is fixed. The head 14 of the pin 10 isretained in the central well 64 of the drum 50 and the neck portion 16passes through the slot 58 between the upper and lower surfaces 60, 62.As the drum 50 is turned further, the underside of the head 14 bearsupon the camming surfaces 66, 68 and, since the pin 10 is fixed in itspanel, the camming surfaces 66, 68 pull the head 14 of the pin 10inwardly towards the center of the drum 50 drawing the two panelstogether in known fashion.

The surfaces 60, 62 forming the upper and lower boundaries of the slot58 may be shaped to cooperate with the curved shape of the neck portion16 of the pin 10.

As can be seen in FIGS. 4 and 5 the camming surfaces 66, 68 are providedwith a number of circumferentially spaced dimples 70 which arecomplementary in shape to the protrusions 22 on the underside of thehead 14 of the pin 10, and are arranged to engage with them when thedrum 50 is rotated.

As the drum 50 is rotated a first diametrically opposed pair of conicalprotrusions 22 on the head 14 will engage with a corresponding pair ofdimples 70 on opposite sides of the slot 58. This engagement provides adegree of lockability, and as the drum 50 is turned further successivepairs of dimples 70 will engage with the same pair of cones 22 on thehead 14 in a ratchet-type movement at the same time as the cammingsurfaces 66, 68 act to pull the pin 10 inwardly, thereby providingsequential locking of the fastening device.

Rotation of the drum 50 can continue until the neck 16 of the pin 10reaches the closed end of the slot 58 furthest from the mouth portion 56or, alternatively, when the two panels being joined come into contactwith one another. When this occurs the pin 10 and drum 50 will be in alocked position because of the engagement of a pair of dimples 70 andcones 22.

The precision required for positioning the recess in the panel which isto receive the drum 50 is less than that required for prior art devices,because the drum does not have just a single, fully-turned, lockedposition. The fastening device of the invention therefore also makes iteasier to avoid a gap between the two panels when the joint istightened, since there is a reduced disadvantage in positioning the drumrecess closer to the edge of the panel than the distance needed to allowthe drum 50 to be turned far enough for the pin 10 to reach the end ofthe slot 58. In the prior art, this would have meant that the drum 50could not lock because it had not fully turned, but in the device of theinvention a locked position can still be achieved even without completeturning of the drum 50.

Sequential locking during rotation of the drum 50 could also be achievedwith a single set of dimples 70 either above or below the slot 58.Because this would result in only one side of the head 14 of the pin 10being subjected to a turning force, rotating the drum 50 tends to twistthe pin 10. If the direction of the thread on the lower part of the pin10 and the side of the slot 58 on which dimples 70 are to be providedare appropriately choosen, the twisting force acting on the head 14 ofthe pin 10 when the drum 50 rotates may be such as to act to tighten thethreaded shank 12 of the pin 10 further into the edge of the panel intowhich it is driven,

The depressions in the camming surfaces 66, 68 have been described asdiscrete dimples. However, the depressions may taken any suitable formand it is envisaged that they may be so shaped and positioned that theymerge, forming essentially a single wave-shaped groove 99 which hasvariable width and depth to engage the protrusions on the head of thepin See FIG. 7.

It is envisaged that the drum 50 described above as having depressionsin one or both of the camming surfaces 66, 68 will be moulded in adie-casting process, preferably in "Mazak". However, it is possible thatthe pin 10 described as having protrusions formed around the undersideof its head 14 may be used in conjunction with a plastic drum. In thiscase the drum need not be provided with depressions in the cammingsurfaces, locking engagement being achieved by the protrusions on thepin biting into the plastic material of the camming surfaces.

As will be apparent various other modifications are possible within theambit of the invention. For example, although described solely inrelation to fastening two panels together substantially at right anglesto one another, it will be appreciated that an adaptation of the abovedescribed embodiment could be used to join panels in other orientations,for instance in edge-to-edge relationship. Also the pin member may bedouble-ended, having a head at each end for cooperation with arespective rotatable drum. In addition, it is possible that the cones orprotrusions are formed in the drum member and the dimples on the head ofthe pin. All such modifications are deemed to be within the broad scopeof the claimed invention.

I claim:
 1. A fastening device for joining two panels togethercomprising:an elongate pin member adapted to be secured in a first oneof said panels, the pin member including a head portion arranged toprotrude from said first panel; and a rotatable drum member adapted forinsertion in a recess in a major surface of the other panel and arrangedto receive said head portion of the pin member, the drum member beingprovided with at least one camming surface arranged to pull the head ofthe pin member inwardly into the drum member when said drum member isrotated and thereby fasten the panels, wherein the head of the pinmember is provided with protrusions or depressions arranged to engagerespective depressions or protrusions provided in a cooperativelydisposed surface of the drum member to facilitate locking engagement ofthe fastening device.
 2. A fastening device according to claim 1,wherein:said locking engagement is provided in a plurality of rotationalpositions of the drum member.
 3. A fastening device according to claim1, wherein:the protrusions or depressions on the head of the pin memberare provided on the underside of the head.
 4. A fastening deviceaccording to claim 1, wherein:the protrusions or depressions on the headof wherein: the protrusions or depressions on the head of the pin memberare arranged to provide a plurality of surface portions on the undersideof the head in a plane substantially perpendicular to the axis of thepin member.
 5. A fastening device according to claim 1, wherein:theprotrusions on the head of the pin member comprise a plurality ofcircumferentially spaced conical protrusions.
 6. A fastening deviceaccording to claim 5, wherein:the angular spacing between each adjacentpair of protrusions on the pin member is substantially 30°.
 7. Afastening device according to claim 1, wherein:said at least one cammingsurface is provided with depressions or protrusions.
 8. A fasteningdevice according to claim 1, wherein:the depressions or protrusions inthe drum member are arranged to provide a plurality of surface portionsin a plane substantially perpendicular to the axis of the pin memberwhen the pin member is in its operative position.
 9. A fastening deviceaccording to claim 1, wherein:the depressions on the drum membercomprise a plurality of circumferentially spaced conical depressions.10. A fastening device according to claim 1, wherein:the depressions onthe drum member comprise a series of linked depressions forming awave-shaped groove.
 11. A fastening device according to claim 1,wherein:the protrusions in the drum member comprise a plurality ofcircumferentially spaced conical protrusions.
 12. A fastening deviceaccording to claim 1, wherein: the drum member is provided with twocamming surfaces each provided with said depressions or protrusions.